The aim of study was determined to relationship between on the seed surface microflora and reaction to Verticillium wilt of cotton cultivars with different gossypol levels. Thirteen cotton cultivars were examined gossypol level and the seed surface microflora of the cotton in vitro. Then, these cultivars were observed susceptibility to non-defoliating (Vd 11 isolate) and defoliating (PYDV6 isolate) pathotypes of Verticillium dahliae Kleb. in vivo. Cultivars were significant at (P <= 0.05) probability level for disease intensity values in vivo and gossypol values in vitro. While the highest gossypol value was determined in "Gloria" cultivar (Gossypium hirsutum L.) with a 1.669 mu g mL(-1) and resistant control "Giza 45" (Gossypium barbadense L.) with a 1.343 mu g mL(-1) the lowest gossypol value was found in "Gossypolsiiz Nazilli" (0.196 mu g mL(-1)) and susceptible control "cukurova 1518" (0.484 mu g mL(-1)) of G. hirsutum L. While the lowest of disease intensity value was observed Vd 11 isolate and PYDV6 isolate in the highest gossypol, resistant control "Giza 45" cultivar (0.30-1.11). The highest disease intensity values were found in the lowest gossypol, "Gossypolstiz Nazilli" cultivar (2.24-2.82) and susceptible control "cukurova 1518" cultivar (2.00-2.63), respectively. Fungus species were isolated in high and low gossypol of cotton seeds at the same rate.